Process of photographic copying by the reflection method



Patented oct. 11, 1921.

UNITED STATES ALFRED MILLER, 01? DESSAU IN ANIIALT, GERMANY,

PATENT oFFlcE.

ASSIGNOR TO I. G. FARBE'N;

INDUSTBIE AKTIENGESELLSCHAFTQOF FRANKFORT-ON-THE-MAIN, GERMANY.

PROCESS OI PEOTOQRAPHIC .COPYING BY THE REFLECTION METHOD.

Application med'uamh as, 1926, sum in.

salt towhic may be 'added a manganese or uranium salt, whllstKogels process depends upon theuse of 'diazo'com ounds. U In all the methods hit erto suggested of producing copies by this kindof process it is necessary to work with verythin ayers, in

order that the possibility of fogging may be restricted, but in spite of this precaution it is not possible to o tain negatives free from objections without a very considerable amount of practice and without depending 25 upon factors the action-of which cannot be controlled.

As distinguished from the known proc-' esses, by the present invention it is possible to' obtain easily negativeswhich are .rich in 3 contrast and are free from fog. The printing forms obtainedyield clear rints'rich in contrast. This result is attaine by applying the treatment which follows the exposure,

for example the colouring for building u the negative only to the surface of the sensitive layer instead oftreating the whole la er as has hitherto been usual. This method as advantages over the known methods. Thus,-

whilst in known methods only very thin la ers are permissible, it is possible in t e method accordin to the invention to vary the thickness of t e layer within wide limits, from 0.001 mm. up to 0.1 mm, or more, since for producing the picture there are utilized only the alterations which occur on the surface of the layer. Moreover, the limits within which the ex osure may be varied, particularly when t icker layers are used, are

much greater than in known processes, and finally the tendency towards appearance of f0 is satisfactorilyavoided.

- The methods hitherto proposed, whether depending u on the use of silver halide emulsions an subsequent chemical develo ment, or upon the use of chromated colloi s,

which is immediately a since the region of the layer a 87,757, and. in Germany November 14, 1924.

iron salts, etc, sufi'er from the defect that in the treatment which follows the exposure, the layer is affected throughout its whole thickness, and therefore the effects of the treatment extend to the portion of the layer jacentto the support onwhich the layer is carried, that is to say, to the portion which during the ex posure has received so much incident li ht that the quantity of reflected light reachm this portion is unable to produce the required eflect- In the known processes hereinbefore referred to, eflorts were made to. counteract this defect at the expense of the contrast and with a restriction in the" limits of the exposure, by using very thin layers. .As come i pared with these processes, thev new process is within practical limits independent of the thickness of the layer, since only the surinto consideration face of the layer comes for the formation of the picture, and the exposure of the parts of the layer which adjoin the support are without influence on the copy or printing form obtained. A

Itis evident that. during the exposure, the greatest difference between the action of incident and of reflected light occurs to the surface of the copying layer, and this is equally true in the case of an unusuall thick layer. Whilst'with the processes use up to now the use of thick layers, in which the sensitizer is distributed throughout the layer and is thus present in the region adjacent to the support, produces a general illumination of this re ion'which impairs the result obtained an reduces the contrast by its tendency to produce a uniform effect over the whole layer, a process which de ends only on the action of light on the sur ace of the layer renders possible and favours the. pro

duction of sharp contrasts and ure lights, d ioining the su port is unaffected by this treatment.

t is to be understood that during exposure fo is produced in the new process as well as in all the processes known up to now, because the sensitizer incorporated in the colloid layer is alteredby the action of light throughout the whole thickness of the layer, but since the fog thus produced is made visible by the after treatment only, the a pear. ance of fog on the copy can be avoided suitable modification of the' after treatment. This modification consists in restrictin the after treatment solely to the-surface o the diminishing the thickness of the lightsen zones "of the layer from building up layer and avoiding the utilization of the lower zones of the colloid layer which are adjacent to the support for building up the picture. The general principle of the present invention may be determined as'follows: Copying by the reflection method without caring for possible fogging, neither by sitive layer nor byother measures, and restricting the after treatment by which the picture is built up merely to the surface of the layer. It is obvious that this general principle may be applied to all light sensitive layers whether they be sensitized by silver halides, chromium salts, iron salts or other sensitizers, Whenever it is possible to strictly limit the after treatment to the surface of the layer and to exclude the lowleir t e picture. Since this is really feasible the principle is ca able of various applications, as will hereina ter appear.

Bythe recess according to the invention it is possi le to produce-a printing surface directly by exposure by reflection. This may, for example,be carriedout in the following manner: A plate or film of transparent material, preferably dyed in order that it may also serve as a light filter, is coated with a colloid layeiywhich is then sensitized by means of a solution of bichromate, which may'contain in addition a catalyst, such as a salt of manganese or ofcopper, and is finally dried. It is then placed in the printing frame with the original to be copied, the colloid layer being adjacent to the original, which may be for instance a black drawing on a white ground, and the exposure is made'from the back through the support. Thus the bichromatized colloid acquires a selective faculty for retaining pigments brought thereon. Pigments may be distributed over the surface of the colloid in the form of a fine powder; preferably the said powder may be dispersed in a fatty medium so as to form a fatty ink well known in the printing art. After washing, drying and moistening with a mixture of water and glycerine, prints may be made with a fatty ink from the fiat printing surface so obtained, whereb a right handed picture is produced in white upon a black ground i. e., the right hand side of the object to be represented corresponds to the right hand side of the picture.

-When using films, it is advantageous to apply a so-called non-curling layer to the back of the film in order to equalize the strains which the sensitive layers exert on the support, particularly when the sensitive layer is relatively thick. These non-curling layers have not been used in the known processes, because the treatment of the exposed layer necessitated the immerslon of the whole picture in the bath, and the non- I is very essential when a negative is concerned.

If it is desired to produce a number of positives from the picture, a print may be made on zinc from the printing surface and may be reversed in known manner and printed in an offset printed machine." A print may also be madefrom the printing surface on, a photolithographic transfer paper and this may be transferred on to zinc, again reversed in known manner, and. prints maybe taken directly from the zinc. The printing surface may also be used as 'a negative, for-which purpose it is soaked 111 water after having been inked with a fatty ink, after which it is dried, and may advantageousl be sprinkled with. bronzepowder in or er to strengthen the covering power. It may then be provided with a very thin coating of lacquer and in this condition may be retouched as desired.

Negatives may also be made in the manner of photolithographic copying by aid of fatty ink. For this purpose the sensitive layer consisting of a colloid adapted to swellis inked with a fatty ink after exposure, and is developed, by washing. The procedure also ma follow that ofalbumenprinting on zin lay using a colloid layer which is soluble in water. To the water there may be added an agent which promocties development such as lactic acid, acetic aci Copies may also be made by spraying a hygroscopic colloid layer with fine powder after the layer has been exposed by the reflection method and breathed upon or similarly treated.

As'colloids there may be'used gelatine. glue, gum arabic, sugar and like substances sensitized for instance by chromates, iron salts, uranium salts.

Figs. 1 and 2 of the accompanying drawings represent sections on an enlarged scale through films embod ing the present invention. Referring to lg. 1, 1 is a supp rt of celluloid or other suitable material an 2 is a layer of a colloid sensitized to light by biin a fatty medium, retained at the areas affected by light. during exposure, 1 and 2 being the support and the sensitized colloid, respectively.

If silver halide emulsions are used, on the surface of the layer a selective deposition of particles of any metal or metal compound from a supersaturated solution thereof must take place. Such a selective deposition is known as physical development; it also occurs when the picture developed chemically is intensified by a physical method.

What I claim is,

1. A process for producing copies by the reflection method wherein the treatment of the sensitized colloid layer after exposure for the purpose of building up the picture is restricted to the surface of said layer.

2. Aprocess for producing copies by the reflection method which consists in treating after exposure the sensitized colloid layer carried on a transparent support in such a manner that the photochemical alterations solely in the surface of said layer are utilized for building up the picture.

3. A process for producing copies by the reflection method which consists in treating after exposure the sensitized colloid layer carried on a transparent flexible support. in such a manner that the photochemical alterations solely in the surface of said layer are utilized for building up the picture.

4:. A process for producin copies by the reflection method which consists in treating after exposure the sensitized colloid layer, carried on a transparent flexible support provided on the back with a colloid layer, in such a manner that the photochemical alterations solely in the surface of the first mentioned layer are utilized for building up the picture.

5. A process for producing copies by the reflection method according to claim 4 which consists in treating after exposure the sensireflection method according to claim-4.- which comprises moistening the surface of the sensitized colloid layer and distributing thereon a fine pigment.

7. A. process for producing copies by the I reflection method according to claim 4 which consists in distributing over the surface of the sensitized colloid layer pigment dispersed in a fatty medium and developing the colloid layer with water.

8. A process for'producing copies by the reflection method according to claim 4, the development of said colloid layer being carried out with water containing an agent which aids the'developing of the layer.

9. A process for producing copies by the reflection method, according to claim 4:, the development of said colloidlayer being carried out with water containing an organic acid.

10. A process for producing co ies by the reflection method. according to c aim 4, the

said colloid layer after having been exposed being inked with a fine pigment dispersed in a fatty medium and spread with a pigment.

1-1. A process for producing copies by thereflection method according to claim 4, the said colloid layer being converted after exposure into a printing surface in the mannor of phototypy.

12. A process for producing copies by the reflection method, according to claim 4, the said colloid layer being converted after exposure into a fiat printing surface by utilizing the swelling properties of the said colloid.

In testimony whereof I afiix my signature.

ALFRED MILLER. 

